The correct answer is - d. casino gambling.
In some parts of the United States, where once the land was of the Native Americans, there a lots of casinos built. Since this casinos are built on a land that was rightfully of the Native Americans, the casinos were obligated to pay the Native Americans, and in general this is performed in a way like paying a monthly or yearly wage in agreement between both sides about the sum that has to be paid. This type of income had made multiple Native American families to be able to live from this money without having to work anything else.